Gripper for coiled tubing injectors

ABSTRACT

The current invention relates to an improved gripper for use within a coiled tubing injector unit. The improved gripper comprises a carrier for securing the gripper to the chain drive mechanism of the coiled tubing injector unit and a gripping shoe carried by the carrier. The improved gripper provides a carrier and a gripping shoe designed to permit quick and easy removal and replacement of the gripping shoe in the field during operation of the coiled tubing injector unit.

RELATED APPLICATIONS

This application claims priority to and is a continuation of U.S. patentapplication Ser. No. 12/550,067 filed on Aug. 28, 2009 now U.S. Pat. No.8,191,620, the entirety of which is incorporated herein by reference.Additionally, this application claims priority to PCT Application No.PCT/US2010/46956 filed on Aug. 27, 2010, the entirety of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

First introduced to oilfield operations in the early 1960's, coiledtubing is now an essential component of hydrocarbon production. Coiledtubing is used in applications ranging from well cleanout to directionaldrilling. Available in sizes ranging from 1″ to 4.5″, coiled tubingstrings are carried on reels and injected into a wellbore using a coiledtubing injector unit. A typical coiled tubing injector unit 5 isdepicted in FIG. 1. The typical unit includes a goose-neck support 3, arotary transmission assembly, parallel drive-chains 7 carrying grippers,skates and a hydraulic system. (The transmission assembly, grippers,skates and hydraulic system are not shown in detail in FIG. 1.) Thoseskilled in the art are familiar with the components and operation of theunit 5 depicted in FIG. 1.

The series of grippers carried by the chains provide the sole directsupport for holding the coiled tubing in place or moving the tubing. Thegrippers are arranged in opposing pairs to secure the coiled tubingstring between the injector-head chains. The hydraulic system appliespressure to the skates which in turn force the grippers toward eachother thereby securing the coiled tubing between the grippers.Additionally, the hydraulic drive system drives the chains to feed thecoiled tubing string into the well or pull the tubing out of the well.

A typical gripper includes a carrier secured to the chain and a grippingshoe supported by the carrier. From time to time, the gripping shoe mustbe replaced due to damage or to accommodate a change in tubing diameteror insertion of a downhole tool. Therefore, a need exists for acarrier/gripping shoe assembly which permits replacement of the grippingshoe without replacing the entire chain assembly.

SUMMARY OF THE INVENTION

The current invention provides a gripper assembly suitable gripping andtransporting coiled tubing. The gripper assembly comprises a carrierhaving an upper surface with at least one arcuate channel. Positioned onthe carrier is a gripping shoe. The gripping shoe has at least onedownwardly extending leg carrying an inwardly projecting tab. The legand inwardly projecting tab cooperates with the carrier to precludelateral movement of the gripping shoe while permitting rotationalmovement of the gripping shoe on the carrier. In the assembled position,the tab cooperates with the carrier to retain the gripping shoe on thecarrier.

In another embodiment, the current invention provides a gripper assemblyfor use in a coiled tubing injector unit. The carrier has an uppersurface with at least two arcuate channels. Positioned on the carrier isa gripping shoe having two downwardly extending legs. Each leg carriesan inwardly projecting tab. The legs and inwardly projecting tabscooperate with the carrier to preclude lateral movement of the grippingshoe while permitting rotational movement of the gripping shoe on thecarrier. In the assembled position, the tabs cooperate with the carrierto retain the gripping shoe on the carrier.

Still further, the current invention provides another embodiment of acoiled tubing gripper assembly. The gripper assembly comprises a carrierhaving an upper surface and at least two outwardly extending lips. Theupper surface has a circular channel. Positioned on the carrier is agripping shoe. The gripping shoe has two downwardly extending legs, eachleg carrying an inwardly projecting tab. The inwardly projecting tabscooperate with the carrier and the outwardly extending lips to precludelateral and vertical movement of the gripping shoe while permittingrotational movement of the gripping shoe on the carrier. In theassembled position, the tabs cooperate with the outwardly extending lipsto retain the gripping shoe on the carrier.

In yet another embodiment, the present invention provides a gripperassembly suitable for supporting coiled tubing. The gripper assemblycomprises a carrier having an upper surface, a first side and a secondside. The first side carries an outwardly extending lip and the secondside carries an outwardly extending lip. The upper surface has tworecessed arcuate channels, wherein each recessed arcuate channel has afirst open end terminating at the first side of the carrier and a secondopen end terminating at the second side of the carrier. The gripperassembly further comprises a gripping shoe positioned on the carrier.The gripping shoe has two downwardly extending legs, each leg carryingan inwardly projecting tab. The inwardly projecting tabs cooperate withthe outwardly extending lips to retain the gripping shoe on the carrier.Preferably, the inwardly projecting tabs cooperate with the carrier andthe outwardly extending lips to preclude lateral and vertical movementof the gripping shoe following assembly while permitting rotationalmovement of the gripping shoe on the carrier during assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a coiled tubing injector unit.

FIG. 2 depicts the drive chain assembly component of FIG. 1.

FIG. 3 is a close up view corresponding to circle A of FIG. 2 anddepicting the improved gripper on the chain assembly.

FIG. 4 is a perspective view of one embodiment of the gripper.

FIG. 5 is an expanded view of FIG. 4 depicting the primary components ofthe gripper.

FIG. 6 is perspective view of the preferred embodiment of the gripper.

FIG. 7 is an expanded view of the preferred embodiment depicted in FIG.6.

FIG. 8 is an expanded view of an alternative embodiment of the currentinvention.

FIG. 9 is a side cutaway view taken along line 9-9 in FIG. 11.

FIG. 10 is a top view of one embodiment of the carrier.

FIG. 11 is a top view of the preferred embodiment of the carrier.

FIG. 12 is a bottom view of the preferred embodiment of the grippingshoe.

FIG. 13 is a top perspective view of the preferred embodiment of thegripping shoe.

FIG. 14 is a bottom perspective view of the preferred embodiment of thegripping shoe.

FIG. 15 is a top view of the gripping shoe.

FIG. 16 is a top view of an alternative embodiment of the carrier.

FIG. 17 is a perspective view of an alternative embodiment of FIG. 16.

DETAILED DISCLOSURE OF THE CURRENT INVENTION

The current invention provides an improved gripper 10, also referred toas a gripper assembly, suitable for use in a conventional coiled tubinginjector unit 5 to grasp and hold coiled tubing. As depicted in FIG. 2,the improved gripper 10 is attached to a conventional drive chain 7.With reference to FIGS. 4 and 5, improved gripper 10 includes a carrier14, a gripping shoe 18 and a pad 74.

The primary components of the preferred carrier 14 are best seen inFIGS. 6-7 and 11. As depicted therein, carrier 14 has a lower surface 21suitable for securing carrier 14 to drive chain 7. The configuration oflower surface 21 is not critical to the current invention. Rather, lowersurface 21 may be any configuration suitable for joining carrier 14 todrive chain 7 as known to those skilled in the art. Further, the mannerof attaching carrier 14 to drive chain 7 is well known to those skilledin the art. The upper surface 22 of carrier 14 includes first and secondsides 26, 30. Each side 26, 30, carries an outwardly extending lip 38.Preferably, lips 38 are 180 degrees apart, i.e. directly across from oneanother. In the preferred embodiment depicted by FIG. 11, upper surface22 has two recessed arcuate channels 42 a, 42 b, each channel having afirst open end 28 terminating at first side 26 and a second open end 32terminating at second side 30. In the currently preferred embodiment, adefined distance, Y, exists between each open end 28 and 32 andoutwardly extending lips 38. Lips 38 may extend outward from uppersurface 22 or may be offset from upper surface such that lips 38 are notflush with upper surface 22. Upper surface 22 also carries a retainingclip 62.

In FIGS. 4-5, retaining clip 62 fits within a pair of slots 64 a, 64 b.In FIGS. 6-7, the preferred embodiment, retaining clip 62 is located ina channel 66 and secured to carrier 14 by a pair of pins 68 a, 68 bpositioned within holes 69 a, 69 b. The manner of securing retainingclip 62 to carrier 14 is not critical provided that retaining clip 62maintains gripping shoe 18 in the desired position as shown in FIGS. 4and 6. In the alternative embodiment of FIG. 8, retaining clip 62includes a tab 62 a. Tab 62 a cooperates with a corresponding recess orslot 62 c in gripping shoe 18 to retain gripping shoe 18 in the desiredposition on carrier 14. In the embodiments of FIGS. 5 and 7, retainingclip 62 lacks tab 62 a. In this embodiment, retaining clip 62 eitherblocks rotational movement of gripping shoe 18 or provides sufficientfrictional contact to maintain gripping shoe 18 in the desired positionon carrier 14.

An alternative embodiment of carrier 14 is depicted in FIG. 10. In thisembodiment, arcuate channels 42 a and 42 b do not extend from first side26 to second side 30. Rather, additional channels 42 c and 42 d providesuitable channels for receiving gripping shoe 18. Regardless of the useof two arcuate channels or four arcuate channels, each channel will haveat least one opening adjacent to extending lips 38. For the purposes ofthis disclosure, the term adjacent refers to that distance defined as Yor less.

Gripping shoe 18 has a concave upper surface 20 configured to gripcoiled tubing. In the assembled configuration, the concave upper surface20 defines the central axis, W, of gripper assembly 10. Thus, asdepicted by FIGS. 3-4 and 6, when gripping shoe 18 is in the assembledposition on carrier 14, outwardly extending lips 38 of carrier 14correspond to the defined central axis W. Accordingly, in the assembledconfiguration, central axis W corresponds to the plane defined byparallel drive chains 7. Additionally, central axis W corresponds to theposition of coiled tubing (not shown) held in place by opposing grippers10 carried by parallel drive trains 7.

The primary components of gripping shoe 18 are best seen in FIGS. 12-14.As depict therein, gripping shoe 18 includes at least two downwardlyextending legs 46, 50. Each leg carries an inwardly projecting tab 54,58. In the preferred embodiment, tabs 54 and 58 have a length, X, whichis greater than the defined distance Y. Thus, in the preferredembodiment, as tabs 54, 58 exit arcuate channels 42 a, 42 b, at least aportion of tabs 54,58 will slide beneath lips 38 prior to tabs 54, 58fully exiting arcuate channels 42 a and 42 b (or if used 42 c and 42 d).Total width, Z, of tabs 54, 58 and respective legs 46, 50, is selectedto permit easy movement of tabs 54, 58 and legs 46, 50 through channels42 a, b, c and d. Finally, gripping shoe 18 preferably includes a recessarea 56 on the side corresponding to retaining clip 62.

Assembly of gripping shoe 18 to carrier 14 is best visualized withreference to the preferred embodiment of FIGS. 2-8 and 11-12. Withcarrier 14 installed on injector chain 7, assembly will require movementof gripping shoe 18 within the plane defined by parallel drive chains 7,i.e. parallel drive chains 7 lay within a common plane. Typically,gripping shoe 18 will be placed on carrier 14 when carrier 14 is locatedon the back portion of chains 7, i.e. the opposite side of chains 7 fromthe area gripping a length of coiled tubing. Installation will requireremoval of the guards (not shown) commonly found on injector unit 5.Assembly requires placement of gripping shoe 18 above and subsequentlyon surface 22 of carrier 14 with legs 46, 50 aligned with arcuatechannels 42 a and 42 b. With gripping shoe 18 positioned on carrier 14in this manner, gripping shoe 18 will contact the upper surface of clip62. Application of sufficient pressure to gripping shoe 18 will depressretaining clip 62. Subsequent rotation of gripping shoe 18 moves legs46, 50 and tabs 54, 58 through channels 42 a and 42 b until tabs 54, 58are below lips 38. If clip 62 includes tab 62 a, then tab 62 a willengage notch or slot 62 c of shoe 18 when in the final assembledposition.

Although the configuration of gripping shoe 18 and carrier 14 permitsrotational movement of gripping shoe 18 on carrier 14 during assembly,the configuration precludes movement of gripping shoe 18 in the lateraldirection during and following installation. Thus, installation ofgripping shoe 18 to carrier 14 requires movement within the plane ofchain assembly 7 and subsequent rotational movement of gripping shoe 18on carrier 14 to the assembled position as depicted in FIG. 6.

As noted above, manufacturing tolerances for gripping shoe 18 andcarrier 14 provide sufficient clearance to permit rotational movement ofgripping shoe 18 on carrier 14. While the preferred configuration wouldpermit rotational movement while establishing contact between tabs 54,58 and lips 38, the typical configuration provides a few thousands of aninch clearance between tabs 54, 58 and lips 38 when gripping shoe 18 isfinally positioned on carrier 14.

Thus, in the preferred embodiment, retaining clip 62, tabs 54, 58 andlips 38 cooperate to secure gripping shoe 18 to carrier 14. Followingpositioning of the tabs 54, 58 beneath lips 38, retaining clip 62 movesto an “up” position adjacent to the recess area 56 on gripping shoe 18,thereby securing gripping shoe 18 in a position suitable for securingcoiled tubing between a pair of grippers 10. As shown in FIGS. 5, 7, 8,10 and 11 retaining clip 62 does not block channels 42 a, 42 b, 42 c or42 d. Further, although preferred, retaining clip 62 may be omitted.

When fully assembled, the coupling mechanism of gripper assembly 10precludes relative movement of gripping shoe 18 within or perpendicularto the common plane defined by parallel drive chains 7.

Removal of gripping shoe 18 requires depression of retaining clip 62 androtation of gripping shoe 18 until the tabs 54, 58 clear lips 38.Gripping shoe 18 is lifted off of carrier 14 within the plane defined byparallel drive chains 7 of coiled tubing injector unit 5.

The above discussion of the assembly of gripping shoe 18 to carrier 14focused on the embodiment of the current invention wherein arcuatechannels 42 a and 42 b provide passage from first side 26 to second side30. One skilled in the art will readily recognize that the assembly ofgripping shoe 18 to carrier 14 having arcuate channels 42 a, 42 b, 42 cand 42 d as depicted in FIG. 10 will be carried out in a similar manner.The only difference when using carrier 14 as depicted in FIG. 10 beingthe limitation on rotational movement.

As depicted in FIGS. 5, 7 and 8, the preferred embodiment of gripper 10includes a pad 74 positioned between carrier 14 and gripping shoe 18.Pad 74 is positioned on surface 22 of carrier 14 prior to assembly. Pad74 may be any convenient polymeric material such as but not limited torubber, nylon, polystyrene, polypropylene and other similarthermoplastic or thermosetting polymers. As known to those skilled inthe art, the compressive force applied by coiled tubing injector unit 5to the coiled tubing (not shown) depends upon the tolerances betweenmachined parts within the unit. Each manufacturing tolerance adds to thedegree of “play” between parts thereby reducing compressive forceapplied to coiled tubing manipulated by the injector unit. Thecompressive nature of pad 74 compensates for necessary tolerancevariations between machined parts thereby evenly transferring tractionforce through gripper assembly 10 to the coiled tubing. Pad 74 alsoreduces the noise generated by the impact of the gripping shoe 18contacting carrier 14 during engagement with a coiled tubing string, notshown. When retaining clip 62, includes tab 62 a, pad 74 will includeslot or notch 62 b to permit engagement of tab 62 a with slot notch 62 cof gripping shoe 18.

In an alternative embodiment depicted in FIGS. 16-17, carrier 114 has anupper body 110. Located within upper body 110 is a circular channel 142.Circular channel 142 defines the outer circumference of an upper surface122. Upper surface 122 includes at least two lips 138 extendingoutwardly above or into channel 142. Lips 138 extend toward outer edge144 of carrier 114. The distance between channel wall 146 and lips 138is sufficient to permit passage of downwardly projecting legs 46, 50 ofgripping shoe 18 while tabs 54, 58 pass beneath lips 138. The remainingcomponents of carrier 114, such as, but not limited to, lower surface121 and channel 166, correspond to the corresponding elements of carrier14 as described above and shown in FIGS. 4-8. Thus, although only oneversion of clip 62 is depicted in FIGS. 16 and 17, any version of clip62 and its associated elements are suitable for use in this embodiment.Further, assembly of gripping shoe 18 to carrier 114 is performed in thesame manner as discussed above with regard to carrier 14 including theaddition of pad 74. Finally, although FIG. 16 depicts a single circularchannel 142, one skilled in the art will recognize that shorter arcuatechannels (not shown) similar to that of FIG. 10 may be substituted forsingle channel 142.

Other embodiments of the current invention will be apparent to thoseskilled in the art from a consideration of this specification orpractice of the invention disclosed herein. Thus, the foregoingspecification is considered merely exemplary of the current inventionwith the true scope and spirit of the invention being defined by thefollowing claims.

1. A gripper assembly comprising: a carrier, said carrier having an upper surface with at least one channel; a gripping shoe positioned on said carrier, said gripping shoe has at least one downwardly extending leg carrying a tab and said gripping shoe has an upper surface configured to grip coiled tubing; wherein said tab cooperates with said carrier to preclude lateral movement of said gripping shoe while permitting rotational movement of said gripping shoe on said carrier and wherein in the assembled configuration, said upper surface of said gripping shoe defines the central axis of said gripper assembly.
 2. The gripper assembly of claim 1, wherein said carrier further comprises: two lips; said carrier has at least two channels; and, wherein said tabs cooperate with said lips to retain said gripping shoe on said carrier.
 3. The gripper assembly of claim 1, wherein said gripper assembly is incorporated into a coiled tubing injector unit.
 4. A gripper assembly comprising: a carrier, said carrier having an upper surface with at least two channels; a gripping shoe positioned on said carrier; said gripping shoe having at least one downwardly extending leg, each leg carrying a tab and said gripping shoe has an upper surface configured to grip coiled tubing; wherein said downwardly extending leg and tab cooperate with said carrier to preclude lateral movement of said gripping shoe while permitting rotational movement of said gripping shoe on said carrier, wherein in the assembled configuration, said upper surface of said gripping shoe defines the central axis of said gripper; wherein in the assembled configuration, said inwardly projecting tabs cooperate with said carrier to retain said gripping shoe on said carrier.
 5. The gripper assembly of claim 4, wherein said tabs cooperate with said channels to retain said gripping shoe on said carrier.
 6. The gripper assembly of claim 4, wherein said carrier further comprises a retaining clip, said retaining clip positioned to preclude rotational movement of said gripping shoe installed on said on said carrier.
 7. The gripper assembly of claim 4, wherein said carrier further comprises a retaining clip said retaining clip carries a tab projecting towards said gripping shoe, said gripping shoe including at least one recess configured to receive said retaining clip, whereby said retaining clip cooperates with said recess to preclude rotational movement of said shoe on said carrier.
 8. The gripper assembly of claim 4, wherein said gripper assembly is incorporated into a coiled tubing injector unit.
 9. A gripper assembly comprising: a carrier; said carrier having an upper surface, said upper surface having two recessed channels; a gripping shoe positioned on said carrier; said gripping shoe having two downwardly extending legs, each leg carrying a tab and said gripping shoe has an upper surface configured to grip coiled tubing; wherein said tabs cooperate with said carrier to preclude lateral and vertical movement of said gripping shoe while permitting rotational movement of said gripping shoe on said carrier, wherein in the assembled configuration, said upper surface of said gripping shoe defines the central axis of said gripper assembly; and, wherein in the assembled configuration, said tabs cooperate with said carrier to retain said gripping shoe on said carrier.
 10. The gripper assembly of claim 9, wherein said carrier further comprises a retaining clip, said retaining clip positioned to preclude rotational movement of a gripping shoe after said gripping shoe is installed on said carrier.
 11. The gripper assembly of claim 9, wherein said carrier further comprises a retaining clip said retaining clip carries a tab, and wherein said gripping shoe further comprises at least one recess configured to receive said retaining clip, whereby said retaining clip cooperates with said recess to preclude rotational movement of said shoe after said gripping shoe is installed on said carrier.
 12. The gripper assembly of claim 9, wherein said gripper assembly is incorporated into a coiled tubing injector unit.
 13. A method of assembling a coiled tubing gripper assembly comprising the steps of: securing a carrier to a coiled tubing injector chain, said coiled tubing injector chain defining a plane; positioning a gripping shoe over said carrier such that gripping shoe is in the plane of said coiled tubing injector tube, said gripping shoe has an upper concave surface configured to grip coiled tubing, the concave surface defining an axis; placing said gripping shoe on said carrier such that said axis is out of alignment with said plane of said chain; rotating said gripping shoe until the axis defined by said upper concave surface corresponds to the plane defined by said chain, thereby securing said gripping shoe to said carrier.
 14. The method of claim 13, wherein placement of said gripping shoe on said carrier substantially precludes lateral movement relative to one another prior to the step of rotating said gripping shoe on said carrier.
 15. The method of claim 13, wherein said step of rotating said gripping shoe on said carrier until the axis defined by said upper concave surface corresponds to the plane defined by said chain, secures said gripping shoe to said carrier in a manner that substantially precludes lateral movement of the grouping shoe relative to the carrier and substantially precludes movement of the gripping shoe within the plane defined by the coiled tubing injector chain.
 16. A method for replacing a coiled tubing injector gripping shoe in a coiled tubing injector assembly said injector assembly comprising a pair of parallel drive chains, each drive chain supporting a plurality of coiled tubing gripper assemblies wherein each assembly comprises a carrier and a gripping shoe, said drive chains defining a plane and said gripping shoe having an upper concave surface defining an axis such that said axis aligns with said plane when said gripping shoe is secured to said carrier, the method comprising the steps of: positioning a gripping assembly having the gripping shoe to be replaced on the back portion of a drive chain; rotating said gripping shoe thereby moving said upper concave surface out of alignment with said plane; lifting said gripping shoe off of said carrier within the plane defined by said parallel drive chains; positioning a replacement gripping shoe within the plane defined by said parallel drive chains with said upper concave surface out of alignment with said plane; placing said replacement gripping shoe on said carrier; rotating said gripping shoe until the axis defined by said upper concave surface aligns with the plane defined by said parallel drive chains.
 17. The method of claim 16, wherein placement of said gripping shoe on said carrier substantially precludes lateral movement relative to one another prior to the step of rotating said gripping shoe on said carrier.
 18. The method of claim 16, wherein said step of rotating said gripping shoe on said carrier until the axis defined by said upper concave surface corresponds to the plane defined by said chain, secures said gripping shoe to said carrier in a manner that substantially precludes lateral movement of the grouping shoe relative to the carrier and substantially precludes movement of the gripping shoe within the plane defined by the coiled tubing injector chain. 